In the process of acquiring seismic data, seismic energy is delivered into the earth. Near surface geology tends to significant affect the seismic energy both going down into the earth and also returning back to the surface. Understanding the near surface geophysical parameters for statics, modeling and coupling would aid geophysicists in their understanding of the subsurface geology through the better interpretation of the seismic data. Several efforts have been made to measure the viscosity and stiffness of the near surface, but the results have been less than satisfactory.
Sercel makes a 432 and 464 vibe controllers that use feedback information from a conventional vibe doing a conventional sweep to make an estimate of the viscosity and stiffness of the near surface geology. The inventors of the present invention have recognized that a limitation of this type of system is that a conventional vibe uses a large baseplate that presses to the ground and the feedback to the Sercel 432 and 464 vibe controller includes all the associated problems of a large baseplate. Issues such as distortion, baseplate flexure, hydraulic limitations like cavitations in the hydraulic lines. While this system provides a reasonable first order guess at the parameters for viscosity and stiffness, improvements in this area would be quite welcome.
In an article published in 2006 by Robert Ley, et al. in Geophysical Prospecting, 2006, 54, 751-762, a helpful discussion of having ground viscosity and stiffness measurements help provide near surface seismic velocity. In this article, there is a description of how the viscosity and stiffness were measured, but it was recognized that current measurement techniques varied significantly from vibe to vibe. The article makes a strong case that better measurement techniques for near surface viscosity and stiffness would be very useful for the industry